A general object of this invention is to provide a new and improved apparatus for repowering and monitoring the traffic on an ESCON serial link. Serial link repowering apparatus introduced earlier provide background information that is useful in understanding our invention.
ESCON originates from the IBM named Enterprise Systems CONnection for serial links via fiber-optic channels. It has become a widely adopted protocol for network communication. It is used by IBM and others. Typical network utilize, IBM's SNA traffic, however other protocols can be supported. IBM has developed protocols and prototypes for T3-capable communications that allow host to host data transfer for MCI Communication Corp. Recently, Hewlett-Packard and Sun Microsystems have joined IBM to promote a Fibre Channel Systems Initiative (FSCI) as a multi-vendor standard for linking host devices with each other and with high capacity storage devices. The proposed Fibre Channel Standard and ESCON are functionally similar. Normally, for IBM compatible systems ESCON is used, while FSCI will be used for channel-speed applications involving incompatible hosts and peripherals. Several Regional Bell Operating Companies (RBOC) have ESCON turnkey services that let users interconnect mainframes and peripherals. The FCSI and ESCON allow the carriers to choose either protocol for functionally similar applications and for channel-extension applications. These channels enable connection to be made for great distances, and between distributed and clustered systems (SYSPLEX).
ESCON, as used herein, refers to a serial connection system in which dynamic connections are established in a serial link between computer system devices. The connections make use of serial links of multi-mode fiber-optic or single-mode fiber-optic pathways. ESCON, as used herein, encompasses the same functions achieved by any fiber channel interface between systems, including the FCSI, which permits a computer system to execute a channel program for data transfers via a serial interface connecting the serial channel with another serial component which conforms, directly or indirectly, to a predetermined protocol for transfers across a right of way between system elements. The right of way is the pathway over which the data transfers via serial links of multi-mode fiber-optic or single-mode fiber-optic ribbons. ESCON is used herein as the common name, since the standard by which this serial connection system was developed was originated by IBM in its Enterprise System CONnection program. As indicated, this program has been expanded, and now allows disparate elements (heterogeneous systems) to be coupled. The current ESCON Architecture is defined by the referenced "IBM Enterprise Systems Architecture/390 ESCON I/O Interface", IBM manual number SA22-7202.
As a protocol, connections are made by the use of frames each having a beginning of frame delimiter, an end of frame delimiter, an identification of the source, and an identification of the destination of the requested connection. The delimiters may initiate a connect or a disconnect operation between the source and the target. The connections are made through a dynamic switch so as to operate the link in one of simplex, half duplex or full duplex modes dependent on the number, direction and type of frames. An example of one of the patents illustrating ESCON is the referenced U.S. Pat. No. 5,107,489, issued Apr. 21, 1992, to P. J. Brown, et al., relating to the "Serial Link Protocol for Forming Dynamic Connections."
In spite of the great advances being made, no one has solved the problems which can originate on right of ways, especially those right of ways that involve common carrier links. Some of those problems, which will be detailed in the detailed description overview have been solved by the present invention, which relates to an ESCON and FSCI type link.
IBM built a very limited number of prototype fiber-optic serial link repowering apparatus during the period 1988 to 1993 with a codename of "PARROT". These PARROT prototypes were installed in a very limited number of customer accounts to solve a specific problem of a single ESCON serial link being shorter than the customer's required distance. The PARROT repeater apparatus repowered the serial bit stream, indicated that no-light was being received in either direction, and offered a remote wrap capability that transmitted what was received from a link back into that same link, including the wrapping of no-light received to no-light transmitted. A PARROT has also been built after our invention to convert from a single-mode (LASER) link to a multi-mode (LED) link. These PARROT apparatus could not indicate that 8/10 code violations (CV's) were being received, that a serial link is being used for transmitting something other than ESCON 8/10 codes (e.g.--voice), could not measure non-idle usage of the link, and could not generate and transmit any serial bit streams for diagnostic purposes.
A serial fiber-optic repeater is commercially available as the IBM multi-port 9032 or 9033 ESCON Director. Configuring a pair of ports as a dedicated or "static" connection would repower the ESCON serial data and could also convert from multi-mode to single-mode similar to the PARROT. Diagnostic capabilities exist for a director port to transmit no-light, idles or any of the four special continuous sequences defined by the ESCON Architecture. The director can also configure a port into remote wrap mode similar to the PARROT, except that a director pod cannot remote wrap no-light received to no-light transmitted. Additionally, the director can detect that CV's are being received to the extent that the ESCON-architected bit-error-rate (BER) threshold has been exceeded, but the director cannot count the exact number of CV's that have been detected. The BER threshold exceeded indication cannot be used to determine whether the serial link is being used to transmit other than ESCON characters. The director is incapable of measuring non-idle usage of the ESCON link.